Origin. Σέξτος ὁ Χαιρωνεύς — second-century Stoic philosopher, native of Chaeronea in Boeotia (central Greece). The name Σέξτος is Latin (the transliteration of Sextus); it indicates Roman citizenship for the family, characteristic of the Greek provincial elite that received the civitas Romana under the Antonines and Hadrian. The family was old, connected with the philosophical house of Chaeronea, and culturally — provincial Greek elite.

Family background: nephew of Plutarch. The most important biographical detail: Sextus is the nephew of Plutarch (Rogovin's footnote ¹⁷ to 01-09). Specifically — the son of one of Plutarch's brothers (presumably Lamprias or Timon; the precise identification in the prosopography is disputed). This means that Sextus grew up in a philosophical household: Plutarch maintained at Chaeronea an academic circle to which relatives, pupils, and guests belonged; he wrote philosophical dialogues in which nephews and sons are often participants. Through this family connection Sextus inherited not the pure Stoic tradition but a mixed one — a Stoic core with the moralist-Platonist baggage of the Plutarchan circle. This accounts for a certain eclecticism in Sextus's philosophical emphases — particularly his interest in the themes of friendship and the family οἶκος, which in Plutarch occupy a central place (De fraterno amore, De amicorum multitudine, De E).

Career: Athens and Rome. He taught at Athens (as did Apollonius before the summons to Rome) and afterwards at Rome — to which he moved, in all likelihood, in the framework of Marcus's educational programme. The precise dating of Sextus's arrival in Rome is not known, but from the fact that Marcus in 01-09 mentions Sextus's house (the πατρονομούμενος οἶκος) as an exemplar, it is plain that Sextus had a settled residence in Rome to which Marcus would come.

Continuing presence: Marcus as emperor. The principal external testimony about Sextus is Dio Cassius 71.1.2: already as emperor, Marcus continued to go to Sextus (and to the rhetor Hermogenes), not ashamed to learn. The anecdote is preserved by Philostratus (Lives of the Sophists II, 1): the philosopher Lucius asked Marcus where he was going and was told: "It is good even for an old man to learn; I am going to the philosopher Sextus to learn what I do not yet know." Marcus apparently kept his teacherly connections in his mature years (cf. Dio's notice about Junius Rusticus, 71.35). The difference in mode: Rusticus was a continuing political counsellor (consul of 162, prefect of the city); Sextus a continuing teacher (school, lectures, no political role).

The lost writings. In Suidas (s. v. Σέξτος, σ 235) the authorship of "Ἠθικῶν Ὑποθετικῶν" in ten books is ascribed to one Sextus the philosopher. If this attribution refers to our Sextus (which is conjectural but not proved), he had a written corpus that has not survived. Note: Sextus the Stoic, the nephew of Plutarch, is not to be confused with Sextus Empiricus (Sextus Empiricus, c. late 2nd – early 3rd century), the principal source on Pyrrhonian scepticism and the author of the Πυρρώνειοι Ὑποτυπώσεις and the Πρὸς μαθηματικούς. These are different people of the same name. Nor is he to be confused with the "Sentences of Sextus" (Sextou Gnōmai) — a Pythagorean-Christian collection of aphorisms variously attributed.

Educational role

Sextus is the third and synthetic of Marcus's principal Stoic mentors. The division of labour among the three:

• Rusticus (01-07): the doctrinal transmitter; corrects the sophistic instinct, hands on Epictetus's Discourses as a canon, teaches accurate reading and slow assent.
• Apollonius (01-08): the existential witness; Marcus sees Stoic ἀπάθεια in action (in pain, in mourning, in illness).
• Sextus (01-09): the social-familial synthesis; the Stoic life within a family, within a circle of friends, in relation to non-philosophers, with the paradox of ἀπαθέστατος + φιλοστοργότατος.

Method: καταληπτικῶς and ὁδῷ. Sextus's unique contribution is methodological: the capacity to work with philosophical δόγματα καταληπτικῶς (with cognitive certainty, in the sense of καταληπτικὴ φαντασία) and ὁδῷ (methodically, step by step). This pair turns Sextus from a "teacher of Stoic convictions" into the systematiser of practical doctrine — he selects the "δόγματα necessary for life" (rather than the whole bulk of school-literature) and arranges them in systematic order for practical use.

The paradox ἀπαθέστατος + φιλοστοργότατος. The principal philosophical-doctrinal find of 01-09 is that Stoic ἀπάθεια is compatible with intense φιλοστοργία (tender love, especially toward one's own). The common (and false) understanding of ἀπάθεια as "coldness" is here refuted by Sextus's living example. This is technically important for the understanding of the Meditations themselves — Marcus writes constantly of love for one's neighbour without any contradiction of his own Stoicism, and Sextus is the exemplar on which the non-paradox was demonstrated for Marcus.

The anti-demonstrative mode. The third paragraph of 01-09 — "εὔφημον ἀψοφητί / πολυμαθὲς ἀνεπιφάντως" — continues the anti-snob programme of Rusticus and Apollonius: Stoic virtue is not displayed socially; it acts inwardly.

• 01-09 — the principal, developed portrait of Sextus.
• 01-17 — the thanksgiving to the gods for "having received good teachers"; Sextus implicitly among them.

• SHA Marcus 3.3 — Sextus among Marcus's principal philosophical teachers.
• Dio Cassius 71.1.2 — Marcus as emperor continues to go to Sextus.
• Philostratus, VS II, 1 — the anecdote of the philosopher Lucius: "It is good even for an old man to learn."
• Suidas s. v. Σέξτος (σ 235) — the attribution of "Ἠθικῶν Ὑποθετικῶν" in 10 books to a Sextus-philosopher (conjectural; not proved to be our Sextus).
• PIR² S 469 — the standard prosopographical entry.
• Plutarch, the literature relating to the family circle at Chaeronea (Quaest. conv., De fraterno amore) — the context of Sextus's family background.
• A. Birley, Marcus Aurelius: A Biography, rev. ed., Routledge, 2000, ch. 3 and passim.
• A. S. L. Farquharson, The Meditations of the Emperor Marcus Antoninus, Oxford 1944, vol. II, ad 1.9 — the standard philological commentary.
• R. Hard, Marcus Aurelius: Meditations, OWC, Oxford 2011, notes ad 1.9.
• P. Hadot, The Inner Citadel, tr. M. Chase, Harvard 1998, ch. 2–3 — the general reconstruction of Marcus's educational biography.
• C. P. Jones, Plutarch and Rome, Oxford 1971 — the reconstruction of the Plutarchan family circle, to which Sextus belonged.